Electric primers have previously been used for the discharge of a variety of military arms, which generally are larger than what are typically considered small arms (0.50 caliber and smaller), such as 20 mm and 0.60 caliber firearms systems. In such conventional electric primers a finite quantity of primer mix is required to reliably activate/ignite the propellant of a round for a given volume of the propellants of different cartridges. The quantity of primer mixes for military ammunition can generally be varied as needed to reliably ignite the secondary propellants given the relatively larger sizes and internal volumes of such 20 mm-0.60 caliber ammunition. In fact, there is excess airspace in the larger primer designs of such ammunition.
In the development of electrically actuated smaller caliber firearms, however, the primer for such calibers is significantly smaller than the existing 20 mm primer used in a variety of military products, i.e., as small as {fraction (1/7)}th the size of 20 mm caliber military electrically activated primers, while the chamber pressures generated in the discharge of such small caliber firearms are generally in a comparable range of approximately 60 kpsi. It therefore has been difficult to provide a commercial small caliber primer of a size appropriate for use in small caliber firearms that can be reliably activated by electrical current and structurally withstand the comparable range of general chamber pressures, but without the risk of activation by undesired sources, such as electrostatic discharge, magnetic fields, electromagnetic radiation, such as that emanating from electrical power lines and transformers and radio frequency transmitters.
The present invention is directed to an electric primer primarily for use in small arms ammunition that functions reliably with such small caliber ammunition. The instant invention provides an electric primer for small arms ammunition generally comprising:
(a) an electrically conductive cup having a bottom with an aperture formed therein;
(b) an electrically conductive explosive within an inner chamber defined within the cup;
(c) an electrically conductive contact positioned between the explosive and the bottom of the cup for transmitting an electric charge to the explosive to initiate the discharge of the explosive, and having a portion extending toward and projecting at least partially into the aperture in the bottom of the cup;
(d) an insulating liner generally received within the cup, separating the cup from the contact, with the insulating liner being formed from polymeric material; and
(e) a retaining means generally positioned over the explosive.
The conductive explosive is configured to form an electrical path between the electrically conductive contact and the cup. The insulating liner further generally is configured to fit between the contact and the cup to retain the electrically conductive contact within the cup after discharge of the explosive. As a result, upon the discharge of the explosive, the electrically conductive contact is reshaped to an extent sufficient to substantially seal the aperture of the cup against leakage of combustion gases created by the discharge of the explosive material.
Various objects, features and advantages of the present invention will become apparent to those skilled in the art upon reading the following specification, when taken in conjunction with the accompanying drawings.